Solid polymer electrolyte and production method

ABSTRACT

An anionically conductive polymer electrolyte, solid at ambient temperature, containing a salt of the formula: 
     
         (R).sub.3 CMX.sub.n, 
    
     wherein M is selected from the group consisting of at least one of boron, phosphorus, antimony, and arsenic, wherein X is halogen, n is 4 or 6, and R is aryl of 6-18 carbon atoms, alkyl of 1-8 carbon atoms, or alkaryl of 7-26 carbon atoms. The polymer is derived from at least one monomer having at least one heteroatom in the monomer unit selected from oxygen, nitrogen, sulfur, and phosphorus. The electrolyte can be prepared by mixing the polymer and the salt together in the presence of a diluent or solvent and removing the diluent or solvent or by polymerizing a salt and monomer mixture utilizing a metal or a Lewis acid catalyst.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of application Ser. No. 895,094, filedAug. 11, 1986 now abandoned which is a continuation of Ser. No. 799,700,filed Nov. 19, 1985, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to primary electrochemical cells utilizing anelectrolyte comprising a solid polymer.

2. Description of the Prior Art

Aqueous electrolytes conventionally used as electrolytes in primarybatteries, can be disadvantageous in that degradation of the electrodescan result by contact with said electrolytes. In addition aqueouselectrolytes can be difficult to handle. Therefore solid electrolyteshave been developed which have certain advantages includingthermostability, absence of corrosion of the electrodes, and a widerange of redox stability which permits their combination with highlyenergizing couples to obtain electrochemical generators of high energyper unit of weight. Solid electrolytes are also advantageous becausethey can be prepared in thin layers which makes it possible to decreasethe internal resistance of the electrochemical generator. Commerciallyavailable solid electrolyte battery systems utilize lithium iodide asthe solid electrolyte since the lighter alkali metals, in particularlithium are the most attractive commercially utilized anode materials.Much research has been concentrated on lithium ion conductors aselectrolytes but only little work has been done using alkaline earthmetal ion conductors since the alkaline earth metal salts are poorlyionized. In a battery, the overall resistance of the fabricatedelectrolyte element limits the rate capability. In addition the volumetaken up by a solid electrolyte such as lithium iodide is wasted spacewhich could otherwise be devoted to active electrode components.Therefore, in order to maximize volumetric energy density and ratecapability, the ability to fabricate a solid electrolyte as a thinelement is important. Because, upon cell discharge, there is often asubstantial redistribution of material in the cell and, in general, anoverall volume change may occur, cell design must accommodate orminimize the stress on a thin, solid electrolyte element. In addition,the electrolyte must be compatible with the electrodes, both in thesense of being unreactive and also of making and maintaining electricalcontact.

Solid polymer-salt complexes for use as electrolytes in electrochemicalgenerators are known from U.S. Pat. No. 4,579,793, Armand at al. inwhich there are disclosed electrolytes of cross linked organometallicpolymers in which lithium salts are dissolved. The solid polymer-saltelectrolytes of U.S. Pat. No. 4,578,326 to Armand et al. are polyethercopolymers which have been found to have improved conductivity overcertain polyether homopolymers. Preferably sodium or lithium salts canbe utilized as the ionic compound to be used in admixture with thepolymer. The solid complexes of poly(ethylene oxide) and magnesiumchloride which are disclosed by Yang et al. in J. ElectrochemicalSociety, July 1986, pp. 1380-1385 appear to be principally anionconductors when used as electrolytes. Cross linked solid polymers of acyclic ether in admixture with alkali metal salts of weak bases aredisclosed in U.S. Pat. No. 4,357,401 to Andre et al. In addition, solidpolymer electrolytes containing a salt the anion of which is a residueof derived from a strong acid and the cation of which is derived from analkali metal or the ammonium ion are disclosed in U.S. Pat. No.4,303,748 to Armand et al.

Novel alkali metal based ionic compounds are disclosed in U.S. Pat. No.4,505,997 to Armand et al. in admixture with solid polymers aselectrolytes. The polymers are derived from monomer units which includeat least one heteroatom, particularly oxygen or nitrogen, in thestructure. Solid electrolytes are disclosed in U.S. Pat. No. 4,556,614to Mehaute et al. which include a first complexing polymer, an ionizablealkaline salt, and a second polymer having cross-linkable functions, forinstance, a polymer of polyoxyethylene containing lithium perchlorate inadmixture with a polymer of an acrylic modified polybutadiene-nitrile.

Complexes of lithium sodium or potassium salts and solid crownpolyethers are disclosed as electrolytes in U.S. Pat. No. 3,704,174 toBerger. In U.S. Pat. No. 4,060,674 and U.S. Pat. No. 4,139,681 toKlemann electrolytes consisting of an organic solvent and anorganometallic alkali metal salt are disclosed.

There is no indication in any of these references that usefulelectrolytes can be obtained from triphenylmethylhalo-borate, -arsenate,-antimonate, or -phosphate salts and solid polymers which provideanionic conductance at ambient temperature, i.e., 20° to 100° C.

It is an object of the invention to provide a solid electrolytecomprising a polymer-salt complex which provides anionic conductance.This is especially important where alkaline earth metal anodes areutilized an electrochemical cells in conjunction with the solidpolymer-salt complex electrolytes since most salt solutions containingsingly charged alkali metal ions are strongly ionized as compared withsalt solutions containing doubly charged alkaline earth metal ions. Thesolid polymer-salt complex electrolytes are suitable for primaryelectrochemical cells operating at ambient temperatures such as 20° to100° C. The electrolytes are particulary useful in combination with analkaline earth metal anode such as an anode of magnesium or calcium. Thepolymer-salt complex electrolytes of the invention have good flexibilityand provide high anionic conductivity when the ionic salt utilized incombination with the solid polymer is an organomethylhalo-borate,-arsenate, -antimonate, or -phosphate compound.

SUMMARY OF THE INVENTION

A polymer-salt complex electrolyte is disclosed which is useful in aprimary electrochemical cell having an anode of an alkali or alkalineearth metal. The electrolyte is capable of providing anionic conductanceand is particularly useful in electrochemical cells having an alkalineearth metal anode which operate at ambient temperatures of about 20° C.to about 100° C. The active cathode material of the cell is selectedfrom at least one of the sulfides, halides, haloborates, haloarsenatesand halophosphates of metals from groups Ib, IIb, IVa, Va, IVb, Vb, VIb,VIIb, and VIII of the Periodic Table of the Elements, quaternarytetraalkylammonium polyhalides, or an element selected from the groupcontaining of sulfur and iodine. The cathode can be, but need not be, acompound which intercalates the cation of which the anode is formed.

A useful method of forming the solid polymer-salt complex electrolyte isto form the polymer from a suitable monomer using a Lewis acid catalystin the presence of an ionizing salt compound which is selected from atleast one of a salt of the formula:

    (R).sub.3 CMX.sub.n,

wherein M is selected from the group consisting of at least one ofboron, phosphorus, antimony, and arsenic, and wherein X is halogen, n is4 or 6, and R is aryl of 6-18 carbon atoms, alkyl of 1-8 carbon atoms,or alkaryl of 7-26 carbon atoms. R is preferably phenyl.

The polymer is formed from a monomer comprising at least one heteroatomin the monomer unit such as a heteroatom selected from at least one ofthe group consisting of oxygen, nitrogen, sulfur, and phosphorus.Alternatively, the polymer-salt complex can be formed by dissolving saidsalt in a preformed polymer either by means of a solvent or by fusiontechniques, if the polymer is thermoplastic.

BRIEF DESCRIPTION OF THE DRAWING

FIGS. 1 and 2 of the drawings show a schematic representation of a cellusing a magnesium anode, one embodiment of a solid electrolyte of theinvention prepared by polymerizing a mixture oftriphenylmethyltetrafluoroborate, magnesium metal and tetrahydrofuran,and a cathode consisting by weight of 50% WS₂, 30% carbon black, and 20%polytetrafluoroethylene powder.

FIG. 3 is a graph showing current densities for a solid polymerelectrolyte when used in a cell operating at normal room temperatureranges or approximately between about 20° C. and about 80° C., using acathode, consisting by weight of 50% WS₂, 30% carbon black and 20%polytetrafluoroethylene powder.

FIG. 4 is a graph showing current densities for one embodiment of thesolid polymer electrolyte of the invention operating at normal roomtemperature ranges using a cathode consisting by weight of 80% CuS and20% polytetrafluoroethylene.

FIG. 5 is a graph showing current densities for a solid polymerelectrolyte operating in a cell at normal room temperature ranges usinga cathode consisting by weight of 50% AgBF₄, 30% graphite and 20%polytetraflurorethylene.

DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENTS

According to the present invention, there is provided an electrolytewhich is a solid at ambient temperature, defined as about 20° C. to 100°C. Said electrolyte comprises an electrolytically active polymer andsalt complex derived from at least one monomer comprising at least oneheteroatom in the monomer unit and said salt is at least one of a saltof the formula:

    (R).sub.3 CMX.sub.n

wherein M is selected from the group consisting of at least one ofboron, phosphorus, antimony, and arsenic, wherein X is halogen, n is 4or 6 and R is aryl of 6-18 carbon atoms, alkyl of 1-8 carbon atoms, oralkaryl of 7-26 carbon atoms. R is preferably phenyl.

The invention provides a solid electrolyte which can be used in aprimary cell assembled, for instance, using a magnesium anode, a cathodecomprised of a mixture of WS₂, graphite or carbon black, andpolytetrafluoroethylene (PTFE). A solid electrolyte is prepared by firstadding a sufficient amount of triphenylmethyltetrafluoroborate ((C₆ H₅)₃CFB₄) to tetrahydrofuran to make a 1 molar solution. Magnesium turningsare added in excess to the mixture while stirring until the (C₆ H₅)₃CBF₄ is completely dissolved and a dark liquid is formed. This liquidpolymerizes to provide a black, rubbery solid polymer of empiricalformula C₇₀ H₁₁₀ MgBF₄ O₁₂. The solid polymer has an electricalconductance of about 10⁻⁴ ohm⁻¹ cm⁻¹ at room temperature.

When this rubbery solid polymer is compressed between a magnesium anodeand a cathode made of WS₂, carbon black, and PTFE powder to form a cell,the cell generates an open circuit potential of about 2 volts, andcurrents of at least about 100 microamperes/cm² can be withdrawn atvoltages greater than 1 volt.

Placing a small piece of the rubbery solid polymer material between a Mgribbon and a piece of copper mesh results in the generation of an opencircuit voltage of about 2 V. The AC conductivity at 1000 Hz of thesolid polymer when compressed between copper and aluminum rods heldapart by a fluoroelastomer O-ring (using externally applied voltage) was9.5×10⁻⁵ ohm⁻¹ cm⁻¹, according to the formula: ##EQU1##

Comparison of the S:W ratio for the used cathode material with that forunused WS₂ indicates a decline from 1.97 to 1.54, and the magnesiumanode was coated with magnesium sulfide. The rubbery solid polymerelectrolyte allowed S⁻⁻ ions formed at the cathode to migrate throughthe electrolyte to the anode. The electrolyte maintained its physicalintegrity as the anode and cathode volumes changed. It is clear fromthis that the solid electrolyte is an anionic conductor rather than theusual cationic conductor.

The polymer which forms a portion of the solid electrolyte of theinvention is generally any homopolymer or copolymer, solid at ambienttemperature, derived from at least one monomer comprising at least oneheteroatom in the monomer unit such as oxygen, nitrogen, sulfur, andphosphorus. Preferred are monomers containing oxygen or nitrogenheteroatoms in the monomer unit and most preferred are the polymers ofcyclic ethers or cyclic acetals such as tetrahydrofuran, 1,3-dioxolane,1,4-dioxane, ethylene oxide, propylene oxide 1,2- or 2,3-butylene oxide.Useful monomer units include: ##STR1## in which R' represents a hydrogenatom or one of the group R₃, --CH₂ --O--R₃, --CH₂ --O--R₄ --R₃, --CH₂--N═(CH₃)₂, with R₃ representing an alkyl or a cycloalkyl radicalincluding particularly 1 to 16, preferably 1 to 5 carbon atoms and R₄representing a polyether radical of the general formula:

    (CH.sub.2 --CH.sub.2 --O).sub.p,

p having a value of 1 to 100, particularly from 1 to 2, or by thefollowing formula: ##STR2## in which R" represents R₃, --R₄ --R₃, withR₃ and R₄ having respectively one of the above-indicated meanings, or bythe following formula: ##STR3## in which R₃ and R₄ have respectively oneof the above indicated meanings, or by the formula: ##STR4## in which R₁and R₂ are identical or different and each represent one of the groupsR₄, R₄ --R₃ with the above meanings, and R₄ can then also represent apolyether of the formula ##STR5## Preferably, the electrolyte comprisesa cyclic ether copolymer particularly one derived from tetrahydrofuranand at least one of ethylene oxide or propylene oxide. The polymer canalso be derived from cyclic acetals such as 1,3-dioxolane and1,4-dioxane. Copolymers of tetrahydofuran and any of the cyclic acetalslisted above are also suitable.

The polymers are preferably formed from the defined monomers in thepresence of a metal or a Lewis acid catalyst. The solid electrolyte canbe formed by adding said salt to a preformed polymer, as defined above,in the presence of a solvent or diluent for said polymer andsubsequently removing said solvent or diluent or by adding said salt tosaid polymer rendered fluid by heating above its melting point. A Lewisacid is any molecule or ion (also called an electrophile) that cancombine with another molecule or ion by forming a covalent bond with twoelectrons from the second molecule or ion. An acid is thus an electronacceptor. Hydrogen ion (proton) is the simplest substance that will dothis, but many compounds, such as boron trifluoride, BF₃, and aluminumchloride, AlCl₃, exhibit the same behavior and are therefore properlycalled acids. Such substances show acid effects on indicator colors andthen dissolved in the proper solvents. Generally, the useful catalystsare selected from the group consisting of metals or metal containingcompounds. The preferred Lewis acid catalysts are metals selected fromthe group consisting of the alkali and alkaline earth metals, aluminum,and zinc. The polyhalides of aluminum, boron, vanadium, tantalumtitanium, zirconium, and niobium are less preferred as catalysts.

As is well known in the prior art, the preferred polyether compounds ofthe invention can be produced by first reacting an initiator compoundhaving active hydrogen atoms. By use of the term "active hydrogen atoms"there is meant any compound which gives a positive Zerewitinoff test.The term active hydrogen atoms is well known and clearly understood bythose skilled in the art. However, to remove any possible ambiguity inthis regard, the term active hydrogen atoms, as used herein includes anyhydrogen atom fulfilling the following two conditions:

(1) It is sufficiently labile to open the epoxide ring of 1,2-propyleneoxide, and

(2) It reacts with methyl magnesium iodide to liberate methane in theclassical Zerewitinoff reaction (see Niederl and Niederl, Micromethodsof Quantitative Organic Analysis, p. 263, John Wiley and Sons, New Yorkcity, 1946).

In utilizing the prior art procedures for making heteric or blockcopolymer polyethers, the 1,2-propylene oxide used therein can bereplaced with tetrahydrofuran. The preferred initiators are those havingup to 3 active hydrogen atoms and one to about eight, most preferablythree (3) to about eight (8), carbon atoms. Representative examples ofsuch compounds are water, monohydric alcohols such as phenol, cresol,ethyl alcohol, methyl alcohol, polyhydric alcohols such as hydroquinone,ethylene glycol, butylene glycol, diethylene glycol, glycerol ortrimethylolpropane. A wide variety of suitable initiators and generalprocedures for making polyethers are illustrated, for instance, in U.S.Pat. Nos. 2,674,619 and 2,677,700, incorporated herein by reference.

As is well known from the prior art, particularly U.S. Pat. No.4,578,326, solid polymers of ethylene oxide, because of the regularoxygen atom sequence in the polymer and the favorable oxygen/carbon atomratio, have good solvation properties with respect to useful ionic saltswhich are dissolved therein so as to provide high conductivities forsuch solid electrolytes. But ethylene oxide polymers have a tendency toform crystalline structures at temperatures even above ambienttemperature; the formation of crystallites occurring more easily as theconcentration of the ionic salt dissolved therein is increased. Theformation of crystallites in ethylene oxide polymers reduces the ionicconductivity of the solid polymer electrolyte and thus renders suchpolymers inappropriate for use at ambient temperatures in electrolyticcells. As disclosed in U.S. Pat. No. 4,578,326, useful polyetherpolymers can be prepared having lower crystallizing temperature andincreased conductivity at ambient temperature than the homopolymers ofethylene oxide by the formation of copolymers of ethylene oxide andmethyl glycidyl ether or propylene oxide. The polymer electrodes of theinvention include homopolymers of substituted and non-substitutedtetrahydrofuran and copolymers of tetrahydrofuran with other cyclicethers as disclosed herein.

The molecular weight of the homopolymers or copolymers forming the solidpolymer electrolyte utilized in the electric current producing primaryelectrochemical cell of the invention is at least about 50,000,preferably the molecular weight is about 100,000 to 1,000,000.

The ionic compound which is utilized in admixture with the polymer of acyclic ether or cyclic acetal in the formation of the solid electrolyteis an ionic compound generally defined as a organohalo-borate-phosphate, -antimonate, or -arsenate having the formula:

    (R).sub.3 CMX.sub.n

wherein M is selected from the group consisting of at least one ofboron, phosphorus, antimony, and arsenic and wherein X is halogen, n is4 or 6, and R is aryl of 6-18 carbon atoms, alkyl of 1-8 carbon atoms,or alkaryl of 7-26 carbon atoms. R is preferably phenyl. Preferably theionic compound salt is incorporated with a suitable monomer or monomersand the mixture polymerized.

Alternatively, the ionic compound salt can be incorporated into apreformed polymer by mixing a solvent or diluent, which is subsequentlyremoved, into the polyether polymer at ambient temperatures so as tosolvate the polymer and thereby allow the incorporation of the ioniccompound salt in admixture with the polymer.

Alternatively, a fusion process can be utilized to incorporate the ioniccompound salt into a preferred polymer. In this process, the polymer israised in temperature until it melts and becomes sufficiently fluid soas to permit the uniform mixture of the ionic compound salt therein.Preferably, the ionic compound salt is incorporated by forming thepolymer from a mixture of at least one monomer and the ionic compundsalt. The concentration of the ionic compound salt in the polymer isgenerally about 0.1 to about 5.0 molar, preferably about 0.5 to about 2molar, and most preferably about 0.5 to about 1.0 molar of the ioniccompound are utilized in admixture with the polymer.

An electric current producing primary electrochemical cell can containan anode comprising an anode active metal selected from group Ia and IIaof the Periodic Table of the Elements, or aluminum. The anode activemetal preferably is an alkali or alkaline earth metal and, mostpreferably is an alkali metal selected from the group consisting ofsodium, potassium, lithium, or an alkaline earth metal, selected fromthe group consisting of magnesium and calcium. The anode active metalmay be present in the anode in the form of an alloy of the metal with atleast one other metal chosen from the groups Ia and IIa of the PeriodicTable of the Elements or zinc or aluminum.

A cathode of the electric current producing primary electrochemical cellhas a cathode active material comprising a compound selected from thegroup consisting of the sulfides, halides, haloborates, andhalophosphates of elements from groups Ib, IIb, IVa, Va, IVb, Vb, VIb,VIIb, and VIII of the Periodic Table of the Elements or an element suchas sulfur or iodine or a tetra-alkylammonium polyhalide, having 1,-6carbon atoms in the alkyl group. While the anode active material can bein the form of a metal or an alloy thereof, as indicated above, thecathode is formed of cathode active materials which can be formed ofcompressed powders which may include a binder and particles of anelectron conductor, such as carbon or graphite, dispersed therein inorder to improve conductivity. The cathode binder can bepolytetrafluoroethylene or other inert polymeric materials known tothose skilled in the art.

Generally, the cathode active materials for a primary electric currentproducing electrochemical cell using the electrolyte of the inventionare composed of those materials which do not give rise to a topochemicalreduction reaction in which the preferred alkali metal or alkaline earthmetal ions find their way into the structure of the cathode and areregenerated by chemical or electrochemical reduction. But the use ofsuch materials as cathode active materials is not excluded. Thematerials which do not give rise to a topochemical reduction reactiongenerally provide considerably higher specific capacities than thosewhich do and therefor these materials are well adapted to themanufacture of high energy density primary cells.

In practice, a primary electric current producing electrochemical cellcan constitute a pile of compressed solid electrolyte pellets eachsuitably sandwiched between a pellet of the anode material and thecathode and separated by a thin film of the solid electrolyte disclosedherein.

In the preparation of the cathode of a primary electric currentproducing electrochemical cell, conventional methods are used in whichpowders of the cathode active material, graphite and/or carbon arepressed together in combination with a binder such aspolytetrafluoroethylene or other polymeric binders known to thoseskilled in the art. Typically, from about 2% to about 30% by weight ofsuch additives are used, including carbon or graphite and thoseadditives employed as binders. The cathodes can be fabricated bypressing a mixture including such additives against a support structuresuch as a nickel or copper wire mesh.

The anode is fabricated in a conventional manner by attaching the anodeactive material to a supporting grid structure made of a material suchas aluminum or nickel.

The following examples illustrate the various aspects of the invention.Where not otherwise specified throughout this specification and claims,temperatures are given in degrees centigrade and parts, percentages, andproportions are by weight.

EXAMPLE 1

A primary electric current producing electrochemical cell was assembledutilizing a magnesium anode and a cathode made by pressing togetherpowdered tungsten disulfide, carbon black and polytetrafluoroethylenepowder. The proportions by weight of the cathode were 50% tungstendisulfide, 30% carbon black, and 20% polytetrafluoroethylene. The solidelectrolyte was prepared by reacting triphenylmethyltetrafluoroboratewith tetrahydrofuran in the presence of magnesium in accordance with thefollowing procedure:

A sufficient amount of triphenylmethyltetrafluoroborate ((C₆ H₅)₃ CBF₄)is added to tetrahydrofuran to make a 1 molar solution. Magnesiumturnings were added in excess to the mixture while it was being stirred.After about 2 hours, the (C₆ H₅)₃ CBF₄ was completely dissolved and adark liquid was formed. This liquid polymerized in about 48 hours toform a black rubbery solid having an electrical conductance of about10⁻⁴ ohm⁻¹ cm⁻¹ at room temperature. The electrolyte is compressed in athin layer between the magnesium anode and the cathode material in adisc area equal to approximately 0.713 cm², as shown by FIG. 1.

After preparing the electrolyte, the activity of the electrolyte wasdetermined by placing a small piece of the solid electrolyte between amagnesium ribbon and a piece of copper mesh. An open circuit voltage ofabout 2.0 V was observed. The conductivity was measured by compressing apiece of the solid electrolyte between copper and aluminum rods heldapart by a fluoroelastomer O-ring. An external voltage is applied acrossthe gap between the two metals to measure the AC conductivity at 1000Hz. The conductivity was 9.5×10⁻⁵ ohm⁻¹ cm⁻¹, according to the formula:##EQU2## S=0.131 cm A=0.519 cm²

^(R) 1000 Hz=2.66K ohm ##EQU3##

The solid electrolyte polymer battery generated an open circuitpotential of about 2 volts, and a current of at least about 100microamperes/cm² Mg were withdrawn at voltages of 1 volt.

Current--Voltage data for this cell was:

    ______________________________________                                        I, microamperes                                                                         i, microamperes/cm.sup.2                                                                     V, volts                                             ______________________________________                                        10        14.0           1.88                                                 20        28.1           1.81                                                 30        42.1           1.69-1.73                                            40        56.1           1.50-1.69    erratic                                 50        70.2           1.46-1.60                                            ______________________________________                                    

The graph of FIG. 3 portrays some of this data.

The current densities shown are good for solid electrolyte cellsoperating at room temperature. While the cell was capable of currentreversal, no evidence of a recharge capability was seen, although thisresulted in an increased open-circuit potential. The cell was thendischarged across a 100 ohm resistor for three days, with the cellvoltage commencing at 0.25 V and slowly falling to 0.03 V at the end ofthis time. The open-circuit potential at this point was 1.49 V, andindicated a slow degradation of either the electrolyte (possible airoxidation), the cathode, or the anode (possible passivation).

The appearance of the cathode and electrolyte were unchanged upon celldisassembly, but the Mg anode was covered with a yellow-white powder.The deposit on the anode surface and the used cathode material wereanalyzed via Energy Dispersive Spectroscopy (EDS), and yielded an X-rayspectrum which showed a comparison of the S:W ratio for the used cathodematerial with that for WS₂ which declined from 1.97 (for WS₂) to 1.54(for used cathode). The anode deposit appeared to be magnesium sulfide.From this data, it is clear that the solid electrolyte allowed S⁻⁻ ionsformed at the cathode to migrate to the magnesium anode and react andtherefore the electrolyte is an anion conductor, as opposed to mostsolid electrolytes (with the exception of F⁻ conductors such as CaF₂)which are anion conductors.

EXAMPLE 2

A battery was assembled as in Example 1, using 80% by weight of CuS and20% by weight of PTFE as the cathode material.

Current density-Voltage data for the first discharge of this battery isas follows:

    ______________________________________                                        i, microamperes/cm.sup.2                                                                        V, volts                                                    ______________________________________                                        0                 1.10                                                        14.0              0.78                                                        28.1              0.58                                                        42.1              0.46                                                        56.1              0.35                                                        70.2              0.24                                                        ______________________________________                                    

After an overnight "charge" @ 3.5 microamperes/cm² the currentdensity-voltage data for the second discharge is:

    ______________________________________                                        i, microamperes/cm.sup.2                                                                        V, volts                                                    ______________________________________                                        0                 1.30                                                        14.0              0.69                                                        28.1              0.39                                                        ______________________________________                                    

The graph of FIG. 4 sets forth the data for this battery using by weight80% CuS/20% PTFE as the cathode material.

The main mode of discharge for this reaction is probably Mg+CuS MgS+Cu.E° for this reaction is 1.5 V. Therefore, the open circuit voltage ofthis cell was somewhat lower than E° for the proposed reaction, and thiscell also polarized more than the Mg/WS₂ cell; therefore, the cathodeappears to be a poorer conductor than the cathode in Example 1. Afterdisassembly, the Mg surface again showed a yellow-white coating, whichlooked identical to that seen in the previous cell, but this coating wasnot analyzed.

An attempt was made to assemble a Mg/S solid electrolyte battery, wherethe cathode was made by making a depression in the end of a 1/2"graphite rod, filling it with powdered graphite, and dripping Sdissolved in CS₂ onto it and allowing the CS₂ to evaporate. While thisproduced an adherent cathode and an open circuit voltage (O.C.V.) of1.29 V, the cell polarized severely.

EXAMPLE 3

A battery was assembled as in Example 1, using 50% by weight of AgBF₄,30% by weight of graphite and 20% by weight of PTFE as the cathodematerial.

Current density--Voltage data for this battery is shown in FIG. 5.

The open circuit voltage and the polarization characteristics werebetter than the cells in Examples 1 and 2, however, after several hours,the voltage became erratic, apparently because of decomposition of thecathode. (The cathode material shows a hygroscopic character afterstanding in air several days).

The cell voltage was still stable during a relatively-high ratedischarge (about 70 microamperes/cm²), but would always become erraticon open circuit or at low discharge rates.

Based upon the above examples, it is apparent that the battery operatesby generating anions at the cathode which are transported through theelectrolyte. The anions react with the Mg anode to form a Mg salt, andelectrons are released to flow through an external circuit.

Preferably, the solid electrolytes of the invention useful in a primarybattery are prepared by adding a sufficient amount of a triphenylmethylcompound from the group (C₆ H₅)₃ CBF₄, (C₆ H₅)₃ CBX₄, (C₆ H₅)₃ CPX₆, (C₆H₅)CSbX₆, and (C₆ H₅)₃ CAsX₆, where X is a halogen, to a suitablemonomer, preferably a cyclic ether, to make a 1 molar solution. A metal,such as alkali or alkaline earth metal turnings, are added in amountsequal to or greater than the quantity of triphenylmethyl compound as themixture is being stirred. The triphenylmethyl compound is completelydissolved in about 2 hours, and this is evidenced by the formation of adark liquid. The liquid is allowed to stand at normal room temperatureranges, whereupon it polymerizes into a black rubbery solid in about 2days. The electrical conductance of these solids is about 10⁻⁴ ohm⁻¹cm⁻¹, which is within the acceptable range of room temperatureoperational solid electrolytes. These can have a conductivity greaterthan about 10⁻³ ohm⁻¹ cm⁻¹ at room temperature down to a conductivity ofabout 10⁻⁷ ohm⁻¹ cm⁻¹.

While any of the mentioned triphenylmethyl compounds are useful, atriphenylmethyltetrahaloborate is preferred. Among thetriphenylmethyltetrahaloborates, triphenylmethyltetrafluoroborate ismost preferred.

In addition to cyclic ethers and cyclic acetals, straight chainaliphatic and aromatic ethers, such as dialkoxyalkanes and acetals areuseful. However, the cyclic ethers and cyclic acetals are preferred.Tetrahydrofuran is most preferred.

While any of the alkali and alkaline earth metals will work as anodes inthe inventive battery, the alkaline earth metals are preferred. Amongthe alkaline earth metals, magnesium and calcium are most preferred.

Normal or surrounding room temperatures, as intended within the purviewof the invention, will range from about 20° C. to about 100° C. and thecapacity of the cell to exhibit anionic conductance is operable when theelectrolyte and cell temperatures are within this range; however, it ispreferred that the temperatures be within the range of between about 25°C. to about 50° C.

It is to be understood that the foregoing disclosure relates tospecifically preferred embodiments of the instant invention, and it isintended to cover in the appended claims all of the variations andmodifications of the invention which do not depart from the spirit andscope of the invention.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows:
 1. An anionically conductivesolid polymer and salt complex electrolyte, solid at a temperature ofabout 20° C. to about 100° C., wherein said polymer and salt electrolytecomprise:A. at least one polymer derived from at least one monomercomprising at least one heteroatom in the monomer unit and B. at leastone ionizing salt comprising a salt of the formula:

    (R).sub.3 CMX.sub.n

wherein M is selected from the group consisting of boron, phosphorus,antimony, and arsenic, X is halogen, n is 4 to 6, and R is aryl of 6-18carbon atoms, alkyl of 1-8 carbon atoms, or alkaryl of 7-26 carbonatoms.
 2. The electrolyte of claim 1 wherein said polymer is derivedfrom monomer units wherein said heteroatom is selected from at least oneof the group consisting of oxygen, nitrogen, sulfur, and phosphorus, andR is phenyl.
 3. The electrolyte of claim 2 wherein said polymer is ahomopolymer or copolymer comprising monomer units derived from at leastone monomer selected from the group consisting of tetrahydrofuran,1,3-dioxolane, 1,4-dioxane, ethylene oxide, propylene oxide, andbutylene oxide.
 4. The electrolyte of claim 3 wherein said polymer isobtained by polymerizing at least one of said monomers in the presenceof at least one initiator compound and a metal or Lewis acid catalyst.5. The electrolyte of claim 4 wherein said M is boron and wherein saidhalogen is fluorine.
 6. The electrolyte of claim 5 wherein said polymercomprises a polymer of tetrahydrofuran or 1,3-dioxolane and saidcatalyst is selected from at least one of an alkali or an alkaline earthmetal, aluminum and zinc.